A vision-testing device of the above-identified type, which is used to examine the crepuscular visual acuity and glare sensitivity, is known from the DE-C-30 03 588. A screen is used in this vision-testing device for examining the crepuscular vision and the dazzle sensitivity, which screen is illuminated by two projectors simultaneously, whereby in the beam path of the one projector there is arranged a visual optotype and the light intensities of both projectors are coupled with one another such that the light intensity of the one projector increases in the same manner as the one of the other projector decreases. This known vision-testing device, which is a clear-vision device, is expensive to make, demands four projectors and many adjustable mirrors in order to create the desired visual sign. This relatively complicated device requires also a large housing and a relatively heavy construction thereby making its transporting ability is limited.
Furthermore vision-testing devices are known from the DE-A 24 09 747 and the DE-A 2 321 570 and have a closed housing, however, do not guarantee clear vision. Moreover these devices demand that a pair of lenses be arranged in front of each eye, which pair of lenses must be very precisely focused so that the visual sign is viewed as a unit and a jump or a shift in the visual sign does not occur. Such devices are, on the one hand, complicated to adjust and are moreover also sensitive to impact so that their transporting ability is limited. It is known from these references to arrange the visual signs on a disk-shaped carrier, which is transilluminated by a light source.
The basic purpose of the invention is to provide a vision-testing device of the above-identified type in such a manner that same is, on the one hand, compact and light and furthermore robust in design, which permits a testing of the crepuscular visual acuity and the dazzle sensitivity, and in addition as a variation to determine the daytime visual acuity or stepped vision values under crepuscular conditions. A further purpose of the invention is to provide a vision-testing device in such a manner that it can be computer-controlled operated and thus the testing input can be significantly reduced.